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Date: Tue, 21 Aug 2012 16:51:23 +0200 From: Miquel van Smoorenburg <mikevs@...all.net> To: stan@...dwarefreak.com CC: David Brown <david.brown@...bynett.no>, Michael Tokarev <mjt@....msk.ru>, Linux RAID <linux-raid@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: O_DIRECT to md raid 6 is slow On 08/20/2012 01:34 AM, Stan Hoeppner wrote: > I'm glad you jumped in David. You made a critical statement of fact > below which clears some things up. If you had stated it early on, > before Miquel stole the thread and moved it to LKML proper, it would > have short circuited a lot of this discussion. Which is: I'm sorry about that, that's because of the software that I use to follow most mailinglist. I didn't notice that the discussion was cc'ed to both lkml and l-r. I should fix that. > Thus my original statement was correct, or at least half correct[1], as > it pertained to md/RAID6. Then Miquel switched the discussion to > md/RAID5 and stated I was all wet. I wasn't, and neither was Dave > Chinner. I was simply unaware of this md/RAID5 single block write RMW > shortcut Well, all I tried to say is that a small write of, say, 4K, to a raid5/raid6 array does not need to re-write the whole stripe (i.e. chunksize * nr_disks) but just 4K * nr_disks, or the RMW variant of that. Mike. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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